The present invention relates to hydraulic shock absorbers of the direct double acting tubular type, and more particularly to an improved piston valving and seal mechanism for this type of shock absorber.
Direct double acting tubular shock absorbers utilized on automotive vehicles having spring-suspended frames usually comprise a cylinder attached to the axle of the vehicle and a piston in the cylinder which is connected with the frame so that when the wheels of the vehicle pass over an uneven surface the piston and cylinder move relative to one another. The cylinder contains a suitable damping fluid which is expelled from one end of the cylinder into a reservoir when the axle and frame move toward one another, relatively. This action is referred to as the compression stroke of the shock absorber. In many instances the valving within the shock absorber is designed to restrict the flow of fluid from the cylinder during the compression stroke and thus restrain the motion of the vehicle. When the cylinder and piston move in the opposite direction, the motion is referred to as recoil. On recoil, it is desirable to cause the damping fluid to freely re-enter the cylinder so that the tendency of the piston to create a vacuum in the cylinder is obviated by the relatively free entrance of fluid into the cylinder.
The present invention is more particularly directed to an improved piston valving and seal assembly of the type which is adapted to control the flow of hydraulic fluid across the piston to and from the compression space of the unit to and from the recoil space of the unit around the periphery of, and through the piston. The improved piston valving and seal mechanism of the present invention importantly provides a new piston seal and valve combination in which the piston seal acts as a check valve preventing fluid from flowing from the rebound chamber through fluted compression passages on the outer periphery of the piston, during the recoil stroke. During recoil the fluid must flow through recoil passages and out into the compression chamber. The recoil valve seat with an orifice impressed therein provides control at low piston velocities. At higher piston velocities, the increase in the differential hydraulic pressure acting on the valve face moves the rebound valve off the seat to accommodate increased fluid flow to the compression chamber.
During the compression stroke, a small portion of fluid flows from the compression chamber through the path created by the recoil orifice through the restriction passage and into the rebound chamber. However, the major portion of the fluid flows from the compression chamber through the fluted compression passages. Again, the differential pressure that exists between the compression chamber and the rebound chamber will tend to lift the piston seal from a seal seat, permitting shock absorber fluid to flow up the fluted passages and into the rebound chamber. A spring biases the piston seal toward its seated position by acting on the seal through a seal retainer.
Accordingly it is an object of the present invention to provide a shock absorber having an improved piston valving and seal assembly of the type described.
Another object of the present invention is to provide a shock absorber having an improved piston valving and seal assembly which is simple in construction, economical to manufacture and effective in operation.
These and other objects of the present invention will become more apparent during the course of the following detailed description and appended claims.
The invention may best be understood with reference to the accompanying drawings, wherein an illustrative embodiment is shown.